SPICEcore and Tunnels

My first trip to South Pole was for the South Pole Ice Core Project, or SPICEcore. We drilled at 1750m deep core, still about 1000m off of the bed, over the 14/15 and 15/16 seasons. The core went back 55 thousand years.

I’ve actually spent a fair bit of time out at SPICEcore this year. We set up a little cargo area out there where we tested radar equipment and drilled some shallow cores. SPICEcore is no longer an area of activity, with only the casing sticking up above the surface. You’d never think that the hole drops more than a mile down into the ice sheet.

We went down into the “tunnels” last weekend, and found this SPICEcore relic. I’ll have another post on the tunnels, but one feature is the different “shrines” that are created in the walls. The SPICEcore glove lives on in infamy! I hadn’t seen this before since I was only part of the first field season and I had forgotten about the pictures I had seen of it – so I was completely surprised to come across the SPICEcore shrine. It’s fun that SPICEcore lives on not just at the core site, but in the tunnel of South Pole station too.

Ice Penetrating Radar

Our main goal this field season is to “image” the West Hercules Dome area. To do this, we use radar. Ice is almost transparent, meaning it doesn’t absorb electrical energy at some frequencies. If this seems unfamiliar to you, think about your microwave. It works really well warming up anything that has water in it, whether an old cup of coffee or the cheese in a quesadilla. But if you’ve ever tried to thaw hamburger meat, you know just how long and poorly that goes. That is because your microwave uses energy at a wavelength that is absorbed by water, which causes it to warm, but not by ice.

Our main radar system, the High Frequency system, uses 3 MHz, so different than your microwave, but a frequency that the ice does not absorb and is able to look all the way through the ice to bed. This actually was first really noticed when airplanes were flying over Greenland on their way to help fight World War II in Europe. And it was a problem. The ice sheet would not reflect the plane’s radar clearly, with some of energy reflecting from the surface, but some reflecting either off the internal layers in the ice or the bed, and arriving later than energy reflected from the surface. This led to crashes as aviators thought they were higher off the surface than they were. But what is a problem for some applications, can be used as an advantage for others.

The HF radar requires a really long set up. There are two antennas, each with two sides that are about 15m long. They need to be separated by about 150 m. A skidoo in front pulls the whole system, and has to be about 50m ahead of the first antenna so it doesn’t create electrical noise. Next comes the “receive” antennas that “listen” for the transmitted signal. The receive antennas are on either side of Siglin sled which has a shelter on it. The radar shelter has a computer in it, which records what the receiver antenna hears and converts it to a digital signal. The “transmit” antenna is at the end of the train. It sends out an electrical wave for the receiver to listen for.

The way the radar works is that “transmitter” sends out a pulse. This pulse travels both across the surface – which is called the direct arrival – and into the ice, where it is reflected by contracts in the ice and at the bed. The “receiver” listens for the direct arrival and when it hears it, it starts recording. We aren’t interested in the direct arrival. What we want is the reflections that occur in the ice. The length of time it takes for the transmitted signal to reach the receiver tells us how deep the reflection occurred, since we know how fast electrical energy travels in ice. So this is how we can determine how thick the ice is and image layers in the ice.

Radar Shelter Towed by Skidoo

Radar Shelter

Receive antenna is a long ways from the transmit antenna

Transmitter Sled

Science at South Pole

I may be giving you the wrong impression about what science at the South Pole is primarily about. Most of the scientific research done here is not glaciology. It’s astronomy. We took a tour of the South Pole Telescope (SPT) a few nights ago. This is one of three main projects using the South Pole to look at Space and way back in time.

Astronomy is not my specialty, so please don’t take my description of what SPT is researching as anything but very rough. SPT is measuring the Cosmic Microwave Background. It slowly moves through the sky looking at the darkest places so that it can see the signature of what happened just after the Big Bang, what is theorized to be a period of inflation.

Apparently, it takes a lot of grease to keep things moving at South Pole temperatures. And the wires have to coiled to allow them tighten as the telescope rotates. Definitely a lot of engineering challenges in all of the science.

This all took place 17 billion years ago, and I thought searching for 1.5 Million year old ice was old. The sensors are actually cooled to nearly absolute zero, where a superconducting metal is used to record the impact of the cosmic microwaves. South Pole is cold, but still about 200 degrees Celsius from absolute zero on cold day.

South Pole is a really good spot for telescopes. It is very cold and high so that there is little atmosphere between the telescope and space. Sure, getting a telescope to South Pole is difficult. But getting one to space is even more challenging. It is also dark a little less than half the year. This leads to long, continuous measurements. There isn’t more total darkness than anywhere else on earth, but only at the Poles is the dark occur for so long.

One of the most fun things about being at South Pole is learning about the different science that is going on. In addition to SPT, there is another project looking at the cosmic microwave background, BICEPS, which collaborates with SPT a lot. There is also a neutrino observatory called ICECUBE, which I hope to tour soon, although it’s sensors are frozen deep into the ice. There is also seismology and atmospheric monitoring going on. Unlike glaciology, most of these are long running projects with observations made year round. South Pole is really a unique location to have a continuously occupied station and the scientific results are really cool!

The New Year means moving the Pole Marker

The geographic South Pole doesn’t move. But the 2800m thick ice sheet does flow at 10 m (30 ft) per year, so relative to the station, it looks like the Pole moves. On January 1^st each year, the geographic pole marker is moved. Last time I came to South Pole, I arrived on January 1^st. The holiday is celebrated on the closest weekend, so it wasn’t a holiday then, which is why I was able to fly on the 1^st and attend the ceremony even though most of my colleagues were out drilling the ice core.

This year New Year’s day was on Sunday, so most of the station turned out for the Pole ceremony. Ceremony may be a little strong – more like tradition. We all formed an irregular arc from the old marker position to the new. Our station manager said a few words, and then we passed the American flag around to the new position. Then we passed the pole marker around, with a hood over the new design.

Each year, the winter-over crew designs and constructs a new marker. This year’s marker featured the stars visible from South Pole station in the winter. At the entrance to the station, each year’s pole marker is displayed. The Pole moving ceremony and the new marker each year is definitely one of my favorite traditions and I’m glad I got to experience it a second time. Last time it was a complete surprise. This time, I was a highlight I had been anticipating.

One additional quirk this year was that the “tourists” came over to watch. There is a tourist camp a few hundred yards from the station for travelers visiting the South Pole. There usually isn’t much interaction between the tourist camp and the station, but particularly not this year with concerns about covid. So this is the first time I’d seen the tourists other than from the galley as they walked to the pole markers. Not surprisingly, when bundled up, I couldn’t tell the difference.

New Year’s Eve Party

Jessie and I are not much of New Year’s Eve partiers. We usually sit on the couch in Park City, try to make it to 10PM to watch the ball drop, and then go to bed to get up for another ski day. But this year the South Pole New Year’s Eve party was pretty amazing. Because of COVID, we held the party outside for the first time. It was awesome.

It was about -30C with -45 wind chill. There was a snow bar serving six different drinks. The coco tamarind old fashioned was delicious. They also mixed up some really good mojitos. There are some unique problems to serving drinks at these temperatures, but the ice melting is not one of them.

There were snow sculptures. And a really steep sledding hill. I took one run, and decided I wanted to remain healthy for the remainder of the season.

I got some frisbee golf in with some of the COLDEX scientists (another project I’m part of).

Fortunately, there was a fire going in an old barrel which allowed us to warm up. We burned the old wood pallets that everything gets shipped up to South Pole on. It was pretty fantastic evening, even if I still only made it to 11PM.

T.J.

South Pole Lake

When the weather isn’t good enough to fly, it’s usually good enough to still do some work around South Pole. So we went a visited South Pole Lake today. My stuffed orca, Ice, thought she’d get to go swimming. Apparently, I forgot to tell her that the South Pole Lake is under 2700 m (approaching 2 miles) of ice.

The lake is actually pretty small. A few kilometers along and across, and about 30m deep. But it’s really cool for a whole bunch of reasons.

First, for glaciology, ice flows differently when on top of water than on top of bedrock or sediment. So we can learn about how ice flows from studying the differences as the ice flows onto, across, and off of the lake.

Second, the lake tells us that the bed is melting. That is, enough heat flows up from the earth’s mantle and crust to melt the base of the ice sheet. Many scientists used to think South Pole was frozen at the bed, but work led by Ben, part of our team, showed that the whole South Pole region is likely melting at the bed. This affects ice flow, but also informs physics experiments.

Third, the lake has lots of sediment below it. We have no idea what these sediments would tell us – which is why I’m going to encourage my colleagues to drill a sediment core in the lake. Maybe we can learn about fluctuations in the size of the East Antarctic ice sheet, and maybe we can learn about millions of years of Antarctic geologic history. Who knows? And the unknown is what excites me!

Fourth, there may be life in the lake. Probably not fish swimming around. But maybe extreme bacteria. Oxygen reaches the lake as the ice melts and releases the trapped gases, so it’s possible there would be a microbial community. Understanding how life might exist in a location like South Pole Lake offers insight into life on other planets.

Despite not being swimmable, South Pole Lake is a cool spot to be able to visit. Its weird to think about lakes existing under ice sheets, but there are actually lots of lakes all around Antarctica. There is a lot of work going into exploring them, and maybe South Pole Lake will get a drilling project soon.

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Hercules Dome

The goal of this season to find where is best to drill an ice core at Hercules Dome. I wrote briefly before about the measurements we are making, but here I will explain what is special about the Hercules Dome region for a deep ice core.

We were not able to fly today because of weather. Basically lots of clouds such that our Twin Otter cannot land easily in the white-on-white. This weather has come up from the West Antarctic ice sheet. WAIS Divide – the location of my first visit to Antarctica where we drilled a 3400m deep ice core – also had flights too and from it cancelled this morning. That’s because most storm system that reach South Pole come inland on the Amundsen Sea coast, up to WAIS Divide, onto Herc Dome, and begin to peter out at South Pole.

This storm pattern is what makes Herc Dome particularly interesting. Herc Dome is located between the East and West Antarctica ice sheets, with ice flowing in all directions. The snowfall at Herc Dome comes primarily from over the West Antarctic Ice Sheet. So Herc Dome “sees” changes in West Antarctica without actually being a part of it. This is important because a main goal of an ice core project is to understand how the West Antarctic Ice Sheet may have changed in the past.

The West Antarctic ice sheet has an ice volume equivalent to about 6 m of global sea level. If WAIS were to collapse, it would raise sea level by about 3 m. That’s because about half of the ice is already below sea level. All of the ice drilled at WAIS Divide when I was there was from below sea level. Having so much ice below sea level makes WAIS potentially unstable because there is a feedback loop – as ice retreats inland, if the bed gets deeper (more below sea level), then the ice flows faster. Then more ice is lost, it retreats to a deeper bed, and more ice is lost – until it collapses.

We don’t know if WAIS collapsed during a previous warm period – called the Last Interglacial – that was about 130,000 years ago. Some evidence suggests it did, some suggests it didn’t. So we want to figure out what the story with WAIS is. If it collapsed in a previous warm period, that’s big deal because 3m of sea level rise puts both my mom’s and my dad’s houses underwater.

Hercules Dome is the best place to drill an ice core to figure this out. As discussed above, it’s climate is influenced by the size of WAIS because the storms pass over it – but the ice wouldn’t go away if WAIS collapsed because it’s not part of WAIS. OK, I realize I may have lost some of you because this isn’t simple stuff – especially if you don’t think about Antarctica every day.

There are other goals of the ice core too, which I can write about more in the future. But for now, think of the Hercules Dome ice core as one of our best tools for figuring out how quickly sea levels change.

Graduate Student Emma with the Radar

Pilots lounging between flights

Field Work

Our field work plans took a big change this year. The US Antarctic Program has unique challenges in dealing with covid given the remoteness and lack of advanced medical care possible so far away from major cities. There was a two week pause on deployments, which went into place 2 days before we were set to depart. We eventually departed about 3 weeks late, but our season had been cut dramatically.

Instead of 30 days of camping, we are now doing 3 weeks of “day trips” to Herc Dome from South Pole. While a major cut, it is still an opportunity to do lots of cool science (and write blog posts with internet access :). Lots of projects have been affected this season, and in a way, we were lucky. We knew of our cuts before we left the US and have not had to pare down our season little bit after little bit.

We were able to start flying with the Twin Otter aircraft last Thursday and will have our last flying day on January 14. On Thursday, we were able to fly to Herc Dome – to an area called West Herc Dome, more on that in another post – with two flights. We took a snow machine (aka skidoo) on each flight, as well as a barrel of gas and some other equipment. So we are now set to start doing research on our next flight there.

On Friday, we flew to Herc Dome again, but a different location called East Herc Dome. This is where my team camped in the 2019/2020 season. They left a lot of stuff there, so we went to retrieve the most valuable items. In this case, it was a 600 lb groomer that gets towed behind a snow machine.

Weather is always a challenge for flights. You need good visibility to land on ungroomed snow surfaces. So we plan on only getting to fly 50% of the days that we are able to. This means that we hope to get 9 flights in the next three weeks. But it could be more, or it could be less. This makes planning a challenge.

Our goal for the next three weeks is to do a detailed survey of West Hercules Dome, which we didn’t get to do in 2019/2020 and is the most promising part of Herc Dome for an ice core. We have lots of other science objectives too, but the survey of this area is the most important. It’s a bit sad that so many scientific objectives won’t be accomplished this year, but on the other hand, it’s really exciting that we can go do any of this work. After two seasons of very little fieldwork, I feel lucky and privileged to have the support from the Antarctic Program to do as much as we can.

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  Twin Otter

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  Team digging out the groomer

Why am I here?

I haven’t written much yet about why I’m here. That is, what science I am working on. So here goes.

I am locating a site for a deep ice core project at Hercules Dome. Hercules Dome is at 86S, 105W, so it’s about 400 km from South Pole. We are using a Twin Otter plane to fly to Herc Dome to make ice-penetrating radar measurements. What is ice penetrating radar? You emit electromagnetic radiation from a transmitting antenna and you “listen” for what comes back on a receiving antenna. Basically, it’s a way to look at and through the ice.

These radar measurements allow us to see a variety of things that we can’t just by looking at the surface. First, we can see the bed of the ice sheet, where ice meets the underlying rock. This usually forms the largest reflection of energy and tells us how thick the ice is.

Second, we can see internal layers in the ice sheet. These layers are caused by acids from volcanic eruptions that fall onto the ice sheet and form layers that are each of one age. The shape of these layers tells us about the past ice flow and whether there are any disturbances that would prevent a continuous climate record from being recovered. The layers near the surface can be used to figure out how much it snows each year. At Herc Dome, is snow between 11 an 15 cm per year of ice equivalent, or about 30-40 cm per year of snow.  This isn’t that much compared to Washington Cascades, but it is relatively high for deep ice coring projects in Antarctica.

Third, we can use radars to measure the vertical ice flow. This is a relatively new technique. It allows us to better estimate how old the ice is with depth. These same radars can also tell us something about how ice crystals are oriented because the radar waves travel faster along some axes of the crystals compared to others.

I use all of this information in an ice flow model. I use the model to try and match the internal layers as best I can with what I know about how the ice flows. The models are never a perfect match because we don’t know exactly how ice deforms or how much it snowed in the past, but we do gain information and confidence in our interpretations by using the models.

I write more later about our progress once we get some new measurements from Herc Dome.

The Poles

We are celebrating Christmas with a two-day weekend – what Jessie would call a golden weekend during med school. The Antarctic work schedule is 6 days a week, with Sunday off.

I went for a cross country ski today. I couldn’t find skate skis, so I went with fish-scale classic skis. At the end of my ski, I stopped by the two Poles. It was my first visit to them this season. Some of you may be thinking the two poles are the geographic and magnetic poles, but no. We are nowhere near the South magnetic pole. Instead, we have a ceremonial pole in addition to the geographic pole.

Why the two? Well, it’s mostly because the ice at the South Pole flows.

The ice sheet here is roughly 2850m thick. It is moving at about 30 ft per year in a direction that is North! (OK, that joke it getting old). It is flowing what we all grid Northwest, with grid indicating the map projection we use such that north is up, south is down, east is east is right, and west is left. This means that geographic pole, which is fixed in space, is not fixed relative to the station and other structures. Since the station is our main reference point, it appears that the geographic pole moves, but in reality it is the station that is moving. There is actually a ceremony each New Year’s Day where the geographic pole marker is moved, so more on that in a week.

Back to the ceremonial pole. It is set right in front of the station and is surrounded by the flags of the nations that signed the inaugural Antarctic treaty. Many more countries have signed since. The ceremonial pole is quite picturesque. The geographic pole is less picturesque because it ends up at different locations within the station area. It currently is pretty close to the vehicle maintenance facility. Pretty cool, but not great for tourist pictures.

Merry Christmas!

T.J.